1. Field of the Invention
The present invention relates to a misfire detecting device of an internal combustion engine capable of detecting a misfire due to an abnormality in an ignition system of an engine or the like.
2. Discussion of Background Formerly, as this kind of device, there is a device which is for instance disclosed in Japanese Unexamined Patent Publication No. 26345/1987. In this disclosure, an inner cylinder pressure of an engine is detected by an inner cylinder pressure sensor, and a crank angle at which the inner cylinder pressure has a peak, is obtained. When this peak position falls in a predetermined crank angle range, the running condition of the engine is judged to be normal.
However, in the conventional device, it is necessary to measure the inner cylinder pressure continuously for each crank angle in a predetermined period. Therefore, the device becomes complicated. The judgment of misfire is difficult to determine in a light load running condition, since the peak of the inner cylinder pressure has two values; one corresponding to a compression top dead center, and the other corresponding to a peak by combustion. Moreover, when the inner cylinder pressure has a peak before the compression top dead center, the judgment of the misfire is impossible.